Disc dryers are large industrial dryers used for drying conveyable or flowable materials such as granular and liquid type products. They typically comprise a hollow shaft carrying hollow annular discs at intervals. Each disc comprises a pair of annular plates welded around the periphery to the shaft. The shaft is formed to have apertures through its wall to the hollow interior of each disc. In operation of the dryer steam is fed through the shaft and passes through the apertures into the hollow region formed by the discs heating the surface of the discs. Material to be dried moves through an inlet formed through an outer casing of the disc dryer and along the length of the shaft where it contacts the outer surfaces of the heated discs thereby drying the material.
As shown in FIG. 5, the discs 41 in a conventional disc dryer 40 have flat surfaces and can be fitted with cross pins 43 that span between the two annular plates 42 forming each disc to prevent the discs from deforming or bursting under steam pressure. At construction of the disc dryer or retrofitting of replacement discs, fitting cross pins to each disc requires drilling or cutting holes through the disc and pressing in and welding of many individual cross pins. This is labour intensive and is carried out when constructing a new disc dryer or retro-fitting an existing dryer with new discs when the existing discs have worn. Other methods for strengthening the discs other than fitting cross-pins are also known in the art but these are also generally labour intensive.
The annular plates for forming discs for disc dryers are typically formed by cutting one or more circular sheets from a square sheet of metal leading to significant scrap metal.
It is an object of the invention to provide an improved disc for use in industrial applications and/or improved disc dryer, or to at least provide the public with a useful choice.